Megajolt for LT1 Optispark Replacement?

paulmon · Post by **paulmon** » Sat Nov 14, 2009 7:59 pm

Optispark is a pain in the butt, so I'm looking for options to remove it all together. Currently weighing going full Megasquirt (time consuming); however I'd prefer to just change the ignition to coilpacks and be done with the Optispark for good leaving the stock computer. I want to drive my car next spring, it's been a slow 2 years with nothing but a handful of test drives. Megasquirt is obviously a good solution, but I want something a little less complicated.

Anyone know if using Megajolt for this is possible? If so how did you interface with the LT1 ECM?

Thanks,

Paul

NITROPIXIE · Post by **NITROPIXIE** » Sat Nov 14, 2009 9:27 pm

That's a pretty awesome locost you have there.

I'm not too familiar with LT1's myself. It depends what type of signal the ecm uses from the optispark as an indication of engine speed. Do you know how it does this?? If its one ground pulse per ignition event then there is a good possibilty they could work together.

If you know of any info pages for the ecu then post up a link and i could give it a look.

paulmon · Post by **paulmon** » Sat Nov 14, 2009 11:29 pm

NITROPIXIE wrote:That's a pretty awesome locost you have there.

I'm not too familiar with LT1's myself. It depends what type of signal the ecm uses from the optispark as an indication of engine speed. Do you know how it does this?? If its one ground pulse per ignition event then there is a good possibilty they could work together.

If you know of any info pages for the ecu then post up a link and i could give it a look.

Thanks Nitropixie. The best source for info I've found on how the Opti works is here:

http://www.gmhightechperformance.com/te ... index.html

There are a few kits to replace the opti, but most don't actually replace it, they simply remove the high voltage from it and still use it as a timing source. Ideally I'm looking to replace the Opti completely, most of the solutions I've found to accomplish that mean replacing the ECM completely which is a little more than I need.

Thanks,

Paul

NITROPIXIE · Post by **NITROPIXIE** » Sun Nov 15, 2009 12:06 pm

From the little i have read i believe that there is no way of replacing the optispark ignition system with megajolt and still keep the original ecm. This is because the signal for the engine position to the ecm is a unique pattern which can't be replicated using a megajolt/edis system.

If an engine speed signal of an ignition event was sent to the ecm then it could of been possible. Is there an ecm for this type of engne that used a std dizzy?? This could be possible.

paulmon · Post by **paulmon** » Mon Nov 16, 2009 1:19 am

NITROPIXIE wrote:From the little i have read i believe that there is no way of replacing the optispark ignition system with megajolt and still keep the original ecm. This is because the signal for the engine position to the ecm is a unique pattern which can't be replicated using a megajolt/edis system.

If an engine speed signal of an ignition event was sent to the ecm then it could of been possible. Is there an ecm for this type of engne that used a std dizzy?? This could be possible.

Yeah, I gave that link a closer read as I suspected the ECM has to go. Oh well.

I would guess I could use the Megajolt much like an MSD 6AL, no? Use the timing off the optispark, but send no power though the opti, but rather just use it for timing out to the ECM. The ECM connects to Megajolt in much the same was as a MSD 6AL would.

NITROPIXIE · Post by **NITROPIXIE** » Mon Nov 16, 2009 8:03 pm

If its the ignition side of things that is a weak point on your engine then you could use it as 2 seperate systems, using the optispark trigger to give speed input for the ecm, then use megajolt to control the ignition side of things. But if its the optispark trigger which is weak point of the whole engine managemnt system then i would look at a way to get rid of this.

Its a shame you couldn't use a VR/hall sensor on the slots of the optispark triggerwheel and have some sort of conditioning circuit to produce an output equivalent to that of the original. This would make it alot more reliable and robust.

paulmon · Post by **paulmon** » Mon Nov 16, 2009 11:19 pm

NITROPIXIE wrote:If its the ignition side of things that is a weak point on your engine then you could use it as 2 seperate systems, using the optispark trigger to give speed input for the ecm, then use megajolt to control the ignition side of things. But if its the optispark trigger which is weak point of the whole engine managemnt system then i would look at a way to get rid of this.

Its a shame you couldn't use a VR/hall sensor on the slots of the optispark triggerwheel and have some sort of conditioning circuit to produce an output equivalent to that of the original. This would make it alot more reliable and robust.

I've been doing a bunch of home work on this and found 6 different options. The general feeling is the high voltage is one of the main contributors to the issues with the Opti, as a pure signaling device it apparently works ok. Two of the solutions use the opti as purely a timing device with a LT1 specific Megajolt type system, 2 replace the ECM and one is an aftermarket replacement opti that's been engineered "better." I'm leaning towards what is called thee LTCC, it changes the engine over to Chevy LSx coils, 1 per cylinder, so no waste spark, but keeps the opti for timing.

Too bad the Megajolt won't work. If you're curious I documented the options on my car's blog at http://www.brutusv8.com/

Cheers,

Paul